Efficient Evaluation of the Number of False Alarm Criterion

This paper proposes a method for computing efficiently the significance of a parametric pattern inside a binary image. On the one hand, a-contrario strategies avoid the user involvement for tuning detection thresholds, and allow one to account fairly for different pattern sizes. On the other hand, a-contrario criteria become intractable when the pattern complexity in terms of parametrization increases. In this work, we introduce a strategy which relies on the use of a cumulative space of reduced dimensionality, derived from the coupling of a classic (Hough) cumulative space with an integral histogram trick. This space allows us to store partial computations which are required by the a-contrario criterion, and to evaluate the significance with a lower computational cost than by following a straightforward approach. The method is illustrated on synthetic examples on patterns with various parametrizations up to five dimensions. In order to demonstrate how to apply this generic concept in a real scenario, we consider a difficult crack detection task in still images, which has been addressed in the literature with various local and global detection strategies. We model cracks as bounded segments, detected by the proposed a-contrario criterion, which allow us to introduce additional spatial constraints based on their relative alignment. On this application, the proposed strategy yields state-of the-art results, and underlines its potential for handling complex pattern detection tasks

Thermal Performance of Insulating Cryogenic Pin Spacers

Following the proposal to introduce an actively cooled radiation screen (5-10 K) for the LHC machine, the design of the LHC cryostat foresees the need for spacers between the cold mass and the radiati on screen. The thermal impedance of the chosen material should be very high and the shape selected to withstrand the contact stress due to the displacements induced by the coll-down and warm-up transi ent. A cryogenic experiment dedicated to studying the thermal behaviour of several proposed spacers was performed at the cryogenics laboratory of CERN before choosing the one to be used for further i nvestigation on the LHC full-scale Cryostat Thermal Model [1] [2]. This paper describes a quantitative analysis leading to the choice of the spacer

Backstreaming of Impurity Gas Through a Leak in Pressurized Vessel

The presence of a leak in a vessel containing pure gas can induce the contamination by atmospheric gas diffusing into the vessel. In order to avoid this, a gas which has to be kept pure also in presen ce of a leak is usually pressurized, to reduce the flow of contaminating gas through the leak owing to the molecular drag by the outstreaming pure gas. In this paper, a simple model calculation of ba ckstreaming based on the solution of the diffusion + drag equation in cylindrical coordinates is presented. It is shown that both the pressure difference and the dimension of the leak are critical in determining the contaminating flow, a maximum in the backstreaming flow appearing when the drag velocity of the outstreaming gas equals the diffusion velocity

instrumental objective measurement of veal calves carcass colour at slaughterhouse

A total of 6700 veal calves were used to compare the ability of chromameter CR300 in measuring the veal meat colour on-line at slaughterhouse and to develop a prediction equation of colour score based on relationship between instrumental and visual assessments. A total of 5000 carcasses were used to develop equation of prediction while 1700 were used to test it. The meat colour was assessed subjectively in 3 different slaughterhouses by the slaughterhouse's judges 10h post mortem and objectively by chromameter CR300 45 post mortem on the Rectus abdominis. The prediction equation classified correctly 79% of carcasses and was characterized by an R2 of 78%. Furthermore it has to be underlined that the chroma contributes to the total R2 with a 0.21 partial R2. This data confirmed that chromameter CR300 can be used on-line to measure objectively veal meat colour at the end of the slaughter line

Thermal Performance of the Supporting System for the Large Hadron Collider (LHC) Superconducting Magnets

The LHC collider will be composed of approximately 1700 main ring superconducting magnets cooled to 1.9 K in pressurised superfluid helium and supported within their cryostats on low heat in-leak column-type supports. The precise positioning of the heavy magnets and the stringent thermal budgets imposed by the machine cryogenic system, require a sound thermo-mechanical design of the support system. Each support is composed of a main tubular thin-walled structure in glass-fibre reinforced epoxy resin, with its top part interfaced to the magnet at 1.9 K and its bottom part mounted onto the cryostat vacuum vessel at 293 K. In order to reduce the conduction heat in-leak at 1.9 K, each support mounts two heat intercepts at intermediate locations on the column, both actively cooled by cryogenic lines carrying helium gas at 4.5-10 K and 50-65 K. The need to assess the thermal performance of the supports has lead to setting up a dedicated test set-up for precision heat load measurements on prototype supports. This paper presents the thermal design of the support system of the LHC arc magnets. The results of the thermal tests of a prototype support made in industry are illustrated and discussed. A mathematical model has been set up and refined by the comparison with test results, with the scope of extrapolating the observed thermal performance to different geometrical and material parameters. Finally, the calculated estimate of the heat load budgets of the support system and their contribution to the total cryogenic budget for an LHC arc are presented

Measurement on Different MLI Systems Between 77 K and 4 K and their Application in Cryogenic Engineering

Precise thermal measurements were done on different types of large surface MLI samples under various boundary conditions. The measurements were focused on the use of MLI for large industrial plants considering quick and simple installation. The results of the measurements aim at optimising MLI parameters, which control the thermal behaviour. Practical recommendations of MLI materials and their installation are given

Evaluating Crowd Density Estimators via Their Uncertainty Bounds

In this work, we use the Belief Function Theory which extends the probabilistic framework in order to provide uncertainty bounds to different categories of crowd density estimators. Our method allows us to compare the multi-scale performance of the estimators, and also to characterize their reliability for crowd monitoring applications requiring varying degrees of prudence

LHC Days

The main scope of this workshop was to address and discuss a number of key topics relative to the current work in the LHC Division, with the aim of improving our understanding of the main issues and identifying lines of further action. An equally important goal was to bring together project engineers who tend to get increasingly busy and specialised, in order to share views and experience

Augmenting Deep Learning Performance in an Evidential Multiple Classifier System

International audienceThe main objective of this work is to study the applicability of ensemble methods in the context of deep learning with limited amounts of labeled data. We exploit an ensemble of neural networks derived using Monte Carlo dropout, along with an ensemble of SVM classifiers which owes its effectiveness to the hand-crafted features used as inputs and to an active learning procedure. In order to leverage each classifier's respective strengths, we combine them in an evidential framework, which models specifically their imprecision and uncertainty. The application we consider in order to illustrate the interest of our Multiple Classifier System is pedestrian detection in high-density crowds, which is ideally suited for its difficulty, cost of labeling and intrinsic imprecision of annotation data. We show that the fusion resulting from the effective modeling of uncertainty allows for performance improvement, and at the same time, for a deeper interpretation of the result in terms of commitment of the decision

Cryogenics for Particle Accelerators and Detectors

Cryogenics has become a key ancillary technology of particle accelerators and detectors, contributing to their sustained development over the last fifty years. Conversely, this development has produced new challenges and markets for cryogenics, resulting in a fruitful symbiotic relation which materialized in significant technology transfer and technical progress. This began with the use of liquid hydrogen and deuterium in the targets and bubble chambers of the 1950s, 1960s and 1970s. It developed more recently with increasing amounts of liquefied noble gases - mainly argon, but also krypton and even today xenon - in calorimeters. In parallel with these applications, the availability of practical type II superconductors from the early 1960s triggered the use of superconductivity in large spectrometer magnets - mostly driven by considerations of energy savings - and the corresponding development of helium cryogenics. It is however the generalized application of superconductivity in particle accelerators - RF acceleration cavities and high-field bending and focusing magnets - which has led to the present expansion of cryogenics, with kilometer-long strings of helium-cooled devices, powerful and efficient refrigerators and superfluid helium used in high tonnage as cooling medium. This situation was well reflected over the last decades by the topical courses of the CERN Accelerator School (CAS). In 1988, CAS and DESY jointly organized the first school on Superconductivity in Particle Accelerators, held at Haus Rissen in Hamburg, where I shared the h. and duty of lecturing on cryogenics with Professor J.L. Olsen of ETH Z rich, while P. Seyfert of CEA Grenoble delivered an evening seminar on superfluidity. This successful school was reiterated in 1995, with cryogenics being addressed by Professor W.F. Vinen of University of Birmingham (superfluidity), as well as J. Schmid (thermodynamics and refrigeration) and myself (superfluid helium technology) of CERN. In the CAS School on Superconductivity and Cryogenics for Particle Accelerators and Detectors held in May 2002 in Erice, Sicily, I am particularly pleased to see a more complete syllabus in cryogenics, most of which is covered by CERN colleagues and published in this report. This is in my view, another sign of the development and vitality of this discipline at CERN, primarily in the LHC division which, by virtue of its mandate and competence, is presently building the largest helium cryogenic system in the world for the Large Hadron Collider and its experiments. I hope this report constitutes a useful source of information and updated reference for our staff dedicated to this formidable endeavour